dm-io.c revision c897feb3dcf3c3300849056ee82b01df7bf66d3c 
1/*
2 * Copyright (C) 2003 Sistina Software
3 *
4 * This file is released under the GPL.
5 */
6
7#include "dm-io.h"
8
9#include <linux/bio.h>
10#include <linux/mempool.h>
11#include <linux/module.h>
12#include <linux/sched.h>
13#include <linux/slab.h>
14
15static struct bio_set *_bios;
16
17/* FIXME: can we shrink this ? */
18struct io {
19	unsigned long error;
20	atomic_t count;
21	struct task_struct *sleeper;
22	io_notify_fn callback;
23	void *context;
24};
25
26/*
27 * io contexts are only dynamically allocated for asynchronous
28 * io.  Since async io is likely to be the majority of io we'll
29 * have the same number of io contexts as buffer heads ! (FIXME:
30 * must reduce this).
31 */
32static unsigned _num_ios;
33static mempool_t *_io_pool;
34
35static unsigned int pages_to_ios(unsigned int pages)
36{
37	return 4 * pages;	/* too many ? */
38}
39
40static int resize_pool(unsigned int new_ios)
41{
42	int r = 0;
43
44	if (_io_pool) {
45		if (new_ios == 0) {
46			/* free off the pool */
47			mempool_destroy(_io_pool);
48			_io_pool = NULL;
49			bioset_free(_bios);
50
51		} else {
52			/* resize the pool */
53			r = mempool_resize(_io_pool, new_ios, GFP_KERNEL);
54		}
55
56	} else {
57		/* create new pool */
58		_io_pool = mempool_create_kmalloc_pool(new_ios,
59						       sizeof(struct io));
60		if (!_io_pool)
61			return -ENOMEM;
62
63		_bios = bioset_create(16, 16);
64		if (!_bios) {
65			mempool_destroy(_io_pool);
66			_io_pool = NULL;
67			return -ENOMEM;
68		}
69	}
70
71	if (!r)
72		_num_ios = new_ios;
73
74	return r;
75}
76
77int dm_io_get(unsigned int num_pages)
78{
79	return resize_pool(_num_ios + pages_to_ios(num_pages));
80}
81
82void dm_io_put(unsigned int num_pages)
83{
84	resize_pool(_num_ios - pages_to_ios(num_pages));
85}
86
87/*-----------------------------------------------------------------
88 * We need to keep track of which region a bio is doing io for.
89 * In order to save a memory allocation we store this the last
90 * bvec which we know is unused (blech).
91 * XXX This is ugly and can OOPS with some configs... find another way.
92 *---------------------------------------------------------------*/
93static inline void bio_set_region(struct bio *bio, unsigned region)
94{
95	bio->bi_io_vec[bio->bi_max_vecs].bv_len = region;
96}
97
98static inline unsigned bio_get_region(struct bio *bio)
99{
100	return bio->bi_io_vec[bio->bi_max_vecs].bv_len;
101}
102
103/*-----------------------------------------------------------------
104 * We need an io object to keep track of the number of bios that
105 * have been dispatched for a particular io.
106 *---------------------------------------------------------------*/
107static void dec_count(struct io *io, unsigned int region, int error)
108{
109	if (error)
110		set_bit(region, &io->error);
111
112	if (atomic_dec_and_test(&io->count)) {
113		if (io->sleeper)
114			wake_up_process(io->sleeper);
115
116		else {
117			int r = io->error;
118			io_notify_fn fn = io->callback;
119			void *context = io->context;
120
121			mempool_free(io, _io_pool);
122			fn(r, context);
123		}
124	}
125}
126
127static int endio(struct bio *bio, unsigned int done, int error)
128{
129	struct io *io;
130	unsigned region;
131
132	/* keep going until we've finished */
133	if (bio->bi_size)
134		return 1;
135
136	if (error && bio_data_dir(bio) == READ)
137		zero_fill_bio(bio);
138
139	/*
140	 * The bio destructor in bio_put() may use the io object.
141	 */
142	io = bio->bi_private;
143	region = bio_get_region(bio);
144
145	bio->bi_max_vecs++;
146	bio_put(bio);
147
148	dec_count(io, region, error);
149
150	return 0;
151}
152
153/*-----------------------------------------------------------------
154 * These little objects provide an abstraction for getting a new
155 * destination page for io.
156 *---------------------------------------------------------------*/
157struct dpages {
158	void (*get_page)(struct dpages *dp,
159			 struct page **p, unsigned long *len, unsigned *offset);
160	void (*next_page)(struct dpages *dp);
161
162	unsigned context_u;
163	void *context_ptr;
164};
165
166/*
167 * Functions for getting the pages from a list.
168 */
169static void list_get_page(struct dpages *dp,
170		  struct page **p, unsigned long *len, unsigned *offset)
171{
172	unsigned o = dp->context_u;
173	struct page_list *pl = (struct page_list *) dp->context_ptr;
174
175	*p = pl->page;
176	*len = PAGE_SIZE - o;
177	*offset = o;
178}
179
180static void list_next_page(struct dpages *dp)
181{
182	struct page_list *pl = (struct page_list *) dp->context_ptr;
183	dp->context_ptr = pl->next;
184	dp->context_u = 0;
185}
186
187static void list_dp_init(struct dpages *dp, struct page_list *pl, unsigned offset)
188{
189	dp->get_page = list_get_page;
190	dp->next_page = list_next_page;
191	dp->context_u = offset;
192	dp->context_ptr = pl;
193}
194
195/*
196 * Functions for getting the pages from a bvec.
197 */
198static void bvec_get_page(struct dpages *dp,
199		  struct page **p, unsigned long *len, unsigned *offset)
200{
201	struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
202	*p = bvec->bv_page;
203	*len = bvec->bv_len;
204	*offset = bvec->bv_offset;
205}
206
207static void bvec_next_page(struct dpages *dp)
208{
209	struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
210	dp->context_ptr = bvec + 1;
211}
212
213static void bvec_dp_init(struct dpages *dp, struct bio_vec *bvec)
214{
215	dp->get_page = bvec_get_page;
216	dp->next_page = bvec_next_page;
217	dp->context_ptr = bvec;
218}
219
220static void vm_get_page(struct dpages *dp,
221		 struct page **p, unsigned long *len, unsigned *offset)
222{
223	*p = vmalloc_to_page(dp->context_ptr);
224	*offset = dp->context_u;
225	*len = PAGE_SIZE - dp->context_u;
226}
227
228static void vm_next_page(struct dpages *dp)
229{
230	dp->context_ptr += PAGE_SIZE - dp->context_u;
231	dp->context_u = 0;
232}
233
234static void vm_dp_init(struct dpages *dp, void *data)
235{
236	dp->get_page = vm_get_page;
237	dp->next_page = vm_next_page;
238	dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
239	dp->context_ptr = data;
240}
241
242static void dm_bio_destructor(struct bio *bio)
243{
244	bio_free(bio, _bios);
245}
246
247/*-----------------------------------------------------------------
248 * IO routines that accept a list of pages.
249 *---------------------------------------------------------------*/
250static void do_region(int rw, unsigned int region, struct io_region *where,
251		      struct dpages *dp, struct io *io)
252{
253	struct bio *bio;
254	struct page *page;
255	unsigned long len;
256	unsigned offset;
257	unsigned num_bvecs;
258	sector_t remaining = where->count;
259
260	while (remaining) {
261		/*
262		 * Allocate a suitably sized-bio: we add an extra
263		 * bvec for bio_get/set_region() and decrement bi_max_vecs
264		 * to hide it from bio_add_page().
265		 */
266		num_bvecs = (remaining / (PAGE_SIZE >> SECTOR_SHIFT)) + 2;
267		bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, _bios);
268		bio->bi_sector = where->sector + (where->count - remaining);
269		bio->bi_bdev = where->bdev;
270		bio->bi_end_io = endio;
271		bio->bi_private = io;
272		bio->bi_destructor = dm_bio_destructor;
273		bio->bi_max_vecs--;
274		bio_set_region(bio, region);
275
276		/*
277		 * Try and add as many pages as possible.
278		 */
279		while (remaining) {
280			dp->get_page(dp, &page, &len, &offset);
281			len = min(len, to_bytes(remaining));
282			if (!bio_add_page(bio, page, len, offset))
283				break;
284
285			offset = 0;
286			remaining -= to_sector(len);
287			dp->next_page(dp);
288		}
289
290		atomic_inc(&io->count);
291		submit_bio(rw, bio);
292	}
293}
294
295static void dispatch_io(int rw, unsigned int num_regions,
296			struct io_region *where, struct dpages *dp,
297			struct io *io, int sync)
298{
299	int i;
300	struct dpages old_pages = *dp;
301
302	if (sync)
303		rw |= (1 << BIO_RW_SYNC);
304
305	/*
306	 * For multiple regions we need to be careful to rewind
307	 * the dp object for each call to do_region.
308	 */
309	for (i = 0; i < num_regions; i++) {
310		*dp = old_pages;
311		if (where[i].count)
312			do_region(rw, i, where + i, dp, io);
313	}
314
315	/*
316	 * Drop the extra reference that we were holding to avoid
317	 * the io being completed too early.
318	 */
319	dec_count(io, 0, 0);
320}
321
322static int sync_io(unsigned int num_regions, struct io_region *where,
323	    int rw, struct dpages *dp, unsigned long *error_bits)
324{
325	struct io io;
326
327	if (num_regions > 1 && rw != WRITE) {
328		WARN_ON(1);
329		return -EIO;
330	}
331
332	io.error = 0;
333	atomic_set(&io.count, 1); /* see dispatch_io() */
334	io.sleeper = current;
335
336	dispatch_io(rw, num_regions, where, dp, &io, 1);
337
338	while (1) {
339		set_current_state(TASK_UNINTERRUPTIBLE);
340
341		if (!atomic_read(&io.count) || signal_pending(current))
342			break;
343
344		io_schedule();
345	}
346	set_current_state(TASK_RUNNING);
347
348	if (atomic_read(&io.count))
349		return -EINTR;
350
351	*error_bits = io.error;
352	return io.error ? -EIO : 0;
353}
354
355static int async_io(unsigned int num_regions, struct io_region *where, int rw,
356	     struct dpages *dp, io_notify_fn fn, void *context)
357{
358	struct io *io;
359
360	if (num_regions > 1 && rw != WRITE) {
361		WARN_ON(1);
362		fn(1, context);
363		return -EIO;
364	}
365
366	io = mempool_alloc(_io_pool, GFP_NOIO);
367	io->error = 0;
368	atomic_set(&io->count, 1); /* see dispatch_io() */
369	io->sleeper = NULL;
370	io->callback = fn;
371	io->context = context;
372
373	dispatch_io(rw, num_regions, where, dp, io, 0);
374	return 0;
375}
376
377int dm_io_sync(unsigned int num_regions, struct io_region *where, int rw,
378	       struct page_list *pl, unsigned int offset,
379	       unsigned long *error_bits)
380{
381	struct dpages dp;
382	list_dp_init(&dp, pl, offset);
383	return sync_io(num_regions, where, rw, &dp, error_bits);
384}
385
386int dm_io_sync_bvec(unsigned int num_regions, struct io_region *where, int rw,
387		    struct bio_vec *bvec, unsigned long *error_bits)
388{
389	struct dpages dp;
390	bvec_dp_init(&dp, bvec);
391	return sync_io(num_regions, where, rw, &dp, error_bits);
392}
393
394int dm_io_sync_vm(unsigned int num_regions, struct io_region *where, int rw,
395		  void *data, unsigned long *error_bits)
396{
397	struct dpages dp;
398	vm_dp_init(&dp, data);
399	return sync_io(num_regions, where, rw, &dp, error_bits);
400}
401
402int dm_io_async(unsigned int num_regions, struct io_region *where, int rw,
403		struct page_list *pl, unsigned int offset,
404		io_notify_fn fn, void *context)
405{
406	struct dpages dp;
407	list_dp_init(&dp, pl, offset);
408	return async_io(num_regions, where, rw, &dp, fn, context);
409}
410
411int dm_io_async_bvec(unsigned int num_regions, struct io_region *where, int rw,
412		     struct bio_vec *bvec, io_notify_fn fn, void *context)
413{
414	struct dpages dp;
415	bvec_dp_init(&dp, bvec);
416	return async_io(num_regions, where, rw, &dp, fn, context);
417}
418
419int dm_io_async_vm(unsigned int num_regions, struct io_region *where, int rw,
420		   void *data, io_notify_fn fn, void *context)
421{
422	struct dpages dp;
423	vm_dp_init(&dp, data);
424	return async_io(num_regions, where, rw, &dp, fn, context);
425}
426
427EXPORT_SYMBOL(dm_io_get);
428EXPORT_SYMBOL(dm_io_put);
429EXPORT_SYMBOL(dm_io_sync);
430EXPORT_SYMBOL(dm_io_async);
431EXPORT_SYMBOL(dm_io_sync_bvec);
432EXPORT_SYMBOL(dm_io_async_bvec);
433EXPORT_SYMBOL(dm_io_sync_vm);
434EXPORT_SYMBOL(dm_io_async_vm);
435